| Background and ObjectiveCurrently,total hip arthroplasty(THA)is an effective surgical treatment option for end-stage hip diseases,which can relieve pain,stabilize the hip joint and restore hip function.While the efficacy of THA has been widely accepted,its complications have also attracted increasing attention.Postoperative instability and dislocation of the hip are the most common complications.The primary cause of joint instability and dislocation after THA is poor implants’ positions,especially the orientation of the acetabular prosthesis.Therefore,how to improve the installation accuracy of acetabular prosthesis has always been a hot and difficult issue.Based on 3D printing pelvis model of the normal developmental hip and developmental dysplasia of the hip(DDH),the acetabular notches and acetabular fossa were used to guide the accurate installation of acetabular prosthesis as anatomical landmarkers in this study,as well as the hip joint biomechanics of the acetabular anatomical reconstruction and nonanatomical reconstruction of Crowe type ⅢDDH in the THA were analyzed by finite element method,which provide theoretical basis and experimental evidence for the accurate installation of acetabular prosthesis and anatomical reconstruction of the acetabulum in THA.Methods1.From September 2018 to October 2020,the pelvic three-dimensional CT data of 25 patients(41 hips)with normal developmental hip were collected in the orthopaedic department of the First Affiliated Hospital of Bengbu Medical College.The data was imported into the Mimics software and used to reconstruct 3D pelvis image.Life-size 3D pelvis models were printed by 3D printing machine.The acetabulum were reamed by the method of total hip replacement on the model.The acetabular cup bottom were placed(15)mm proximal from and(1-5)mm over the proximal line of the anterior and posterior acetabular notches respectively to determine cup inclination.The acetabular cup bottom were placed(1-5)mm pronation and supination at the proximal point of acetabular posterior notch respectively to determine cup anteversion.Plain radiographs of the pelvis were taken and the GeoGebraGeometry software was used to measure the inclination and anteversion of the acetabular cup at 22 positions.The data was collected and analyzed statistically.2.From September 2018 to December 2020,the pelvic three-dimensional CT data of 22 patients(36 hips)with DDH were collected in the orthopaedic department of the First Affiliated Hospital of Bengbu Medical College.The data was imported into the Mimics software and used to reconstruct 3D pelvis image.Life-size 3D pelvis models were printed by 3D printing machine.The morphology of the acetabular fossa and notches were restored by removing the osteophytes.The acetabulum were reamed by the method of total hip replacement on the model.The acetabular cup bottom were placed(1-5)mm proximal from and(1-5)mm over the proximal line of the anterior and posterior acetabular notches respectively to determine cup inclination.The acetabular cup bottom were placed(1-5)mm pronation and supination at the proximal point of acetabular posterior notch respectively to determine cup anteversion.Plain radiographs of the pelvis were taken and the GeoGebraGeometry software was used to measure the inclination and anteversion of the acetabular cup at 22 positions.The data was collected and analyzed statistically.3.One patient with end-stage left hip arthritis secondary to Crowe type Ⅲ DDH was selected in this study,who accepted total hip arthroplasty in the orthopaedic department of the First Affiliated Hospital of Bengbu Medical College in April 2020.This patient was female,57 years old.The preoperative and postoperative pelvis 3D CT were performed.Thirteen acetabular cup models with different anteversion,inclination and rotation center height were established in the Mimics and 3-Matic software.The boundary and load conditions were set in the Abaqus software,the calculation was carried out.The Von Mises and stress distribution of the hip joint were observed.Results1.In normal developemental hip,the intraoperative "safe zone" of acetabular prothesis inclination in THA was(-3mm-+1mm),that is,the lower edge of the acetabular cup was 3 mm invaginate-1mm over the proximal line of the anterior and posterior acetabular notches(the average inclination were(35.10±3.22)°-(45.90±2.68)°).The optimal inclination of the acetabular cup could be obtained when the lower edge of the acetabular cup was 1mm invaginate into the proximal line of the anterior and posterior acetabular notches(the average inclination was(40.71±2.80)°).The intraoperative "safe zone" of acetabular prothesis anteversion in THA was(-1mm-+1mm),that is,the lower edge of the acetabular cup was 1mm pronation-1mm supination at the proximal point of acetabular posterior notch(the average anteversion were(13.34±2.89)°-(21.87±2.51)°).The optimal anteversion of the acetabular cup could be obtained when the lower edge of the acetabular cup was parallel to the proximal line of the anterior and posterior acetabular notches(the average anteversion was(18.00±1.64)°).2.In DDH,the intraoperative "safe zone" of acetabular prothesis inclination in THA was(-2mm-+1mm),that is,the lower edge of the acetabular cup was 2mm invaginate1mm over the proximal line of the anterior and posterior acetabular notches(the average inclination were(35.06±3.35)°-(41.64±3.51)°).The optimal inclination of the acetabular cup could be obtained when the lower edge of the acetabular cup was parallel to the proximal line of the anterior and posterior acetabular notches(the average inclination was(41.64±3.51)°).The intraoperative "safe zone" of acetabular prothesis anteversion in THA is(-2mm-0mm),that is,the lower edge of the acetabular cup were 2mm supination-1mm pronation at the proximal point of acetabular posterior notch(the average anteversion were(10.67±4.55)°-(20.86±4.44)°).The optimal anteversion of the acetabular cup could be obtained when the lower edge of the acetabular cup was 1mm supination at the proximal point of acetabular posterior notch(the average anteversion was(14.58±3.83)°).3.In the Crowe type Ⅲ DDH THA,if the hip rotation center was restored anatomically,the Von Mises of the acetabulum,acetabular cup and polyethylene liner were lowest when the anteversion and inlcination of acetabular cup were 15°,35° respectively;If the anteversion and inlcination of acetabular cup were 15°,40°,the Von Mises of the acetabulum,acetabular cup and polyethylene liner were lowest when the rotation center migrated 10mm proximally.In all 13 models,the Von Mises of the acetabulum,acetabular cup and polyethylene liner were lowest when the anteversion and inlcination of acetabular cup were 15°,35° respectively,as well as the rotation center was restored anatomically.ConclusionsIn total hip arthroplasty for normal developed hip and DDH,both acetabular notches and acetabular fossa can be used as anatomical landmarks to guide the accurate installation of acetabular prosthesis.The concept of intraoperative "safe zone" helps surgeons to install the acetabular prosthesis safely in THA.In total hip arthroplasty for Crowe type Ⅲ DDH,the anatomical reconstruction center of rotation,15° anteversion and 35° inclination of the acetabular cup were suggested,simultaneously bone graft above the acetabular cup and additional screws will further reduce the Von Mises of hip joint. |
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